SGX attestation validation (#232)

- Added message parsing capabilities to HSMCertificateV2ElementSGXQuote
- Added file certificate loading capabilities to HSMCertificateV2ElementX509
- Factored out common behavior between ledger and SGX attestation verification into helper library functions
- Added helper library for assorted attestation utils, including a v5+ attestation message parsing class
- Added SGX do_verify_attestation function with its corresponding module
- Added verify_attestation operation to adm_sgx tool
- Added and updated unit tests
- Ignoring long line warnings for test attestation utils resources module

middleware/adm_sgx.py

@@ -31,6 +31,7 @@
 from admin.pubkeys import do_get_pubkeys
 from admin.changepin import do_changepin
 from admin.sgx_attestation import do_attestation
+from admin.verify_sgx_attestation import do_verify_attestation
 
 
 def main():
@@ -42,12 +43,13 @@ def main():
         "pubkeys": do_get_pubkeys,
         "changepin": do_changepin,
         "attestation": do_attestation,
+        "verify_attestation": do_verify_attestation,
     }
 
     parser = ArgumentParser(description="SGX powHSM Administrative tool")
     parser.add_argument("operation", choices=list(actions.keys()))
     parser.add_argument(
-        "-r",
+        "-p",
         "--port",
         dest="sgx_port",
         help="SGX powHSM listening port (default 7777)",
@@ -61,7 +63,7 @@ def main():
         help="SGX powHSM host. (default 'localhost')",
         default="localhost",
     )
-    parser.add_argument("-p", "--pin", dest="pin", help="PIN.")
+    parser.add_argument("-P", "--pin", dest="pin", help="PIN.")
     parser.add_argument(
         "-n",
         "--newpin",
@@ -103,6 +105,26 @@ def main():
         f"{DEFAULT_ATT_UD_SOURCE}). Can also specify a 32-byte hex string to use as"
         " the value.",
     )
+    parser.add_argument(
+        "-t",
+        "--attcert",
+        dest="attestation_certificate_file_path",
+        help="Attestation key certificate file (only valid for "
+        "'verify_attestation' operation).",
+    )
+    parser.add_argument(
+        "-r",
+        "--root",
+        dest="root_authority",
+        help="Root attestation authority (only valid for 'verify_attestation' "
+        "operation). Defaults to Intel SGX's root authority.",
+    )
+    parser.add_argument(
+        "-b",
+        "--pubkeys",
+        dest="pubkeys_file_path",
+        help="Public keys file (only valid for 'verify_attestation' operation).",
+    )
     parser.add_argument(
         "-v",
         "--verbose",

middleware/admin/attestation_utils.py

@@ -0,0 +1,143 @@
+# The MIT License (MIT)
+#
+# Copyright (c) 2021 RSK Labs Ltd
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+# of the Software, and to permit persons to whom the Software is furnished to do
+# so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+import hashlib
+import json
+import re
+import secp256k1 as ec
+import requests
+from pathlib import Path
+from comm.cstruct import CStruct
+from .misc import AdminError
+from .certificate_v2 import HSMCertificateV2, HSMCertificateV2ElementX509
+
+
+class PowHsmAttestationMessage(CStruct):
+    """
+    pow_hsm_message_header
+
+    uint8_t platform 3
+    uint8_t ud_value 32
+    uint8_t public_keys_hash 32
+    uint8_t best_block 32
+    uint8_t last_signed_tx 8
+    uint8_t timestamp 8
+    """
+
+    HEADER_REGEX = re.compile(b"^POWHSM:(5.[0-9])::")
+
+    @classmethod
+    def is_header(kls, value):
+        return kls.HEADER_REGEX.match(value) is not None
+
+    def __init__(self, value, offset=0, little=True, name="powHSM"):
+        self.name = name
+        # Parse header
+        match = self.HEADER_REGEX.match(value)
+        if match is None:
+            raise ValueError(
+                f"Invalid {self.name} attestation message header: {value.hex()}")
+
+        # Validate total length
+        header_length = len(match.group(0))
+        expected_length = header_length + self.get_bytelength()
+        if len(value[offset:]) != expected_length:
+            raise ValueError(f"{self.name} attestation message length "
+                             f"mismatch: {value[offset:].hex()}")
+
+        # Grab version
+        self.version = match.group(1).decode("ASCII")
+
+        # Parse the rest
+        super().__init__(value, offset+header_length, little)
+
+        # Conversions
+        self.platform = self.platform.decode("ASCII")
+        self.timestamp = int.from_bytes(self.timestamp, byteorder="big", signed=False)
+
+
+def load_pubkeys(pubkeys_file_path):
+    # Load the given public keys file into a map
+    try:
+        with open(pubkeys_file_path, "r") as file:
+            pubkeys_map = json.loads(file.read())
+
+        if type(pubkeys_map) != dict:
+            raise AdminError(
+                "Public keys file must contain an object as a top level element")
+
+        result = {}
+        for path in pubkeys_map.keys():
+            pubkey = pubkeys_map[path]
+            try:
+                pubkey = ec.PublicKey(bytes.fromhex(pubkey), raw=True)
+            except Exception:
+                raise AdminError(f"Invalid public key for path {path}: {pubkey}")
+            result[path] = pubkey
+        return result
+    except (FileNotFoundError, ValueError, json.JSONDecodeError) as e:
+        raise AdminError('Unable to read public keys from "%s": %s' %
+                         (pubkeys_file_path, str(e)))
+
+
+def compute_pubkeys_hash(pubkeys_map):
+    # Compute the given public keys hash
+    # (sha256sum of the uncompressed public keys in
+    # lexicographical path order)
+    if len(pubkeys_map) == 0:
+        raise AdminError("Can't compute the hash of an empty public keys map")
+
+    pubkeys_hash = hashlib.sha256()
+    for path in sorted(pubkeys_map.keys()):
+        pubkey = pubkeys_map[path]
+        pubkeys_hash.update(pubkey.serialize(compressed=False))
+    return pubkeys_hash.digest()
+
+
+def compute_pubkeys_output(pubkeys_map):
+    pubkeys_output = []
+    path_name_padding = max(map(len, pubkeys_map.keys()))
+    for path in sorted(pubkeys_map.keys()):
+        pubkey = pubkeys_map[path]
+        pubkeys_output.append(
+                f"{(path + ':').ljust(path_name_padding+1)} "
+                f"{pubkey.serialize(compressed=True).hex()}"
+            )
+    return pubkeys_output
+
+
+def get_root_of_trust(path):
+    # From file
+    if Path(path).is_file():
+        return HSMCertificateV2ElementX509.from_pemfile(
+            path,
+            HSMCertificateV2.ROOT_ELEMENT,
+            HSMCertificateV2.ROOT_ELEMENT)
+
+    # Assume URL and try to grab it
+    ra_res = requests.get(path)
+    if ra_res.status_code != 200:
+        raise RuntimeError(f"Error fetching root of trust from {path}")
+    return HSMCertificateV2ElementX509.from_pem(
+        ra_res.content.decode(),
+        HSMCertificateV2.ROOT_ELEMENT,
+        HSMCertificateV2.ROOT_ELEMENT)

middleware/admin/certificate_v2.py

@@ -20,9 +20,12 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
+import re
+from pathlib import Path
 import base64
 from .certificate_v1 import HSMCertificate
 from .utils import is_nonempty_hex_string
+from sgx.envelope import SgxQuote
 
 
 class HSMCertificateV2Element:
@@ -105,7 +108,10 @@ def signature(self):
         return self._signature.hex()
 
     def get_value(self):
-        return self.custom_data
+        return {
+            "sgx_quote": SgxQuote(self._message),
+            "message": self.custom_data,
+        }
 
     def to_dict(self):
         return {
@@ -170,6 +176,21 @@ def to_dict(self):
 
 
 class HSMCertificateV2ElementX509(HSMCertificateV2Element):
+    @classmethod
+    def from_pemfile(kls, pem_path, name, signed_by):
+        return kls.from_pem(Path(pem_path).read_text(), name, signed_by)
+
+    @classmethod
+    def from_pem(kls, pem_str, name, signed_by):
+        return kls({
+            "name": name,
+            "message": re.sub(r"[\s\n\r]+", " ", pem_str)
+                         .replace("-----END CERTIFICATE-----", "")
+                         .replace("-----BEGIN CERTIFICATE-----", "")
+                         .strip().encode(),
+            "signed_by": signed_by,
+        })
+
     def __init__(self, element_map):
         self._init_with_map(element_map)